How to know that any other key except certain was pressed

Question

When I'm writing a php program I often face the following situation:

step 1: '[' pressed:
Result:
[<cursor>

step 2: ']' pressed
Result:
[]<cursor>

step 3: move the cursor between '[]':
Result:
[<cursor>]

My idea was to save 1 keystroke and do step 3 automatically when '[]' sequence was pressed.

Currently I did the following:

;flag to signal us the '[' was pressed
(defvar *kb--bracket-pressed* nil)
;activate flag
(defun bracket-pressed ()
      "[ key pressed"
      (interactive)
      ;activate flag
      (setq *kb--bracket-pressed* t)
      (insert "[")
      )

(defun back-bracket-pressed ()
      "] key pressed"
      (interactive)
      (when *kb--bracket-pressed*
            (insert "]")
            (backward-char 1)
            ;deactivate flag
            (setq *kb--bracket-pressed* nil)
            )
      )

;when php-mode is activated
(local-set-key (kbd "[") 'bracket-pressed)
(local-set-key (kbd "]") 'back-bracket-pressed)

The problem is: I don't know how to reset the flag to nil, when any other key except "]" was pressed after "[".

Answer 1

To save the keystrokes I created the following. I found that pretty often I have to type: [''], which requires 4 keystrokes. So, I desided to add the following rules:

step 1. "[" pressed: 
    print "["
    ;output looks like: "[<cursor>"

step 2. "[" pressed for the 2-nd time. 
    output "'']"; 
    move cursor 2 characters to the left 
   ;output looks like: "['<cursor>']"
step 3. "[" pressed for the 3-rd time: 
    delete 1 character backwards
    delete 1 character forward
   ;output looks like: "[]"

Code:

(defvar *kb--bracket-pressed* 0)

;this function is called when any other characted except "[" is pressed 
(defun clean-bracket-pressed ()
      (when (and
                  (not (= *kb--bracket-pressed* 0))
                  (not (string= (this-command-keys) "[")
                        ))
            (setq *kb--bracket-pressed* 0)
            )
      )

;this function is called when "[" is pressed 
(defun bracket-pressed ()
      "[ key pressed"
      (interactive)
      (cond
            ((= 0 *kb--bracket-pressed*)
                  (insert "[")
                  (setq *kb--bracket-pressed* (1+ *kb--bracket-pressed*))
                  )
            ((= 1 *kb--bracket-pressed*)
                  (insert "'']")
                  (backward-char 2)
                  (setq *kb--bracket-pressed* (1+ *kb--bracket-pressed*))
                  )
            ((= 2 *kb--bracket-pressed*)
                  (delete-char -1)
                  (delete-char 1)
                  (setq *kb--bracket-pressed* 0)
                  )
            )
      )

(defun my-php-mode ()
  "My php-mode customisations."
  (local-set-key (kbd "[") 'bracket-pressed)
  (add-hook 'pre-command-hook 'clean-bracket-pressed nil 'make-it-local)
)

(add-hook 'php-mode-hook 'my-php-mode)